1) Field of the Invention
The present invention relates to a vacuum process device, and in particular relates to a method of transporting semiconductor processed members (hereinafter, wafers) between process chambers and the like in a semiconductor process device.
2) Description of the Related Arts
A semiconductor process device, and in particular a device that processes wafers that are a process subject in a reduced pressure has been required to be more efficient in processing the process subject as processes become more minute and refined. As a result, in recent years, a multi-chamber device provided with a plurality of process chambers connected therein has been developed, and improvements have been made to make productivity per installation area of a clean room more efficient. In such a device that performs processes with a plurality of process chambers provided therein, a gas in each process chamber and the pressure are adjusted to a reduced pressure, and a transport chamber provided with a robot and the like for transporting wafers is connected thereto.
As such a multi-chamber device, a device with a cluster tool structure in which process chambers are connected radially along circumferences of transport chambers is widely used. However, the cluster tool type device requires a large installation area, and in particular the installation area has been becoming further larger as wafers are becoming larger in diameters in recent years. To address this problem, a device with a linear tool structure has appeared (for example, Japanese Unexamined Patent Application Publication No. 2007-511104). A characteristic of a linear tool is that the structure has a plurality of transport chambers, a process chamber is connected to each transport chamber, and the transport chambers are connected with each other directly or with spaces for receiving and passing wafers (hereinafter, buffer rooms) therebetween.
Although the linear tool structure has been proposed to make an installation area smaller, other proposals have been made to further improve productivity. Shortening of a process time and efficient transportation are important in improving productivity, and in particular many efficient transport methods have been proposed. Known representative methods use scheduling. The methods using scheduling are that a transport operation is decided in advance, and transportation is performed based on the decision. In an example of methods proposed, a transport operation is decided by allocating earlier, as a transport destination, a process chamber with a shorter process completion time (for example, Japanese Patent Application Laid-open Publication No. 10-189687).
The methods using scheduling can realize high productivity under a condition that lengths of time for etching and deposition are stable around standard lengths of time required for the processes. However, a process time often is not stable and becomes severalfold longer than standard lengths of time required for the processes when a new product is processed or processing conditions for wafers change. In such a situation, when a process time is extended in a process chamber among a plurality of process chambers, a wafer planned to be processed in the process chamber cannot be transported as scheduled, and has to wait in the device; as a result, a transport path of another wafer planned to be processed in another process chamber is blocked, and thus productivity is decreased.
Explaining specifically, for example, suppose that there are two process chambers, a process in a process chamber A is planned to end in 20 seconds, and a process in a process chamber B is planned to end in 50 seconds. At this time, it is supposed that a wafer W1 planned to be processed next in the process chamber A is waiting in a load lock. If the process in the process chamber A ends in 20 seconds as scheduled, the wafer W1 is taken out of the load lock, and the process is performed on the wafer W1 in the process chamber A. If this is the case, the load lock is emptied, and a wafer W2 to be processed next in the process chamber B can be taken in; accordingly, as soon as a process in the process chamber B ends, the wafer W2 can be processed in the process chamber B. However, if the process in the process chamber A does not end in 20 seconds as scheduled, the wafer W1 waiting in the load lock remains occupying the load lock, and the wafer W2 cannot enter the load lock. Accordingly, the process in the process chamber A is prolonged, and even if the process in the process chamber B ends earlier, the wafer W2 planned to be processed next in the process chamber B cannot be transported to the process chamber B, and cannot be processed. Therefore, productivity decreases.
As a solution for a case that a wafer planned to be processed in a process chamber is not transported as scheduled, and interferes with transportation of another wafer planned to be processed in another process chamber, a method of, when a wafer that cannot be transported as scheduled emerges, rescheduling a transport schedule by collecting a wafer that is not transported as scheduled or moving the wafer to a space for temporary evaluation has been proposed (Japanese Unexamined Patent Application Publication No. 2002-506285).